Rotating machinery, including motors, generators and the like, are widely used in manufacturing, power generation and materials processing, among other applications. Due at least in part to the extended duration of use and high rotational speeds (e.g., revolutions per minute (RPM)) at which industrial rotating machines typically operate, such machines are subject to wear and potential failure. In order to minimize catastrophic damage, the machines are often taken offline to perform scheduled maintenance, such as lubrication and/or replacement of parts, as a precaution. However, such preventative machinery maintenance can be costly, in terms of facility downtime and replacement parts and labor expenses.
Consequently, it has become more cost-effective to monitor the operational status of rotating machinery using such metrics as machine vibration to provide an indication of its condition. One type of condition monitoring device is a two-wire proximity transmitter system that converts a non-linear eddy current signal, obtained from a suitable current probe, into a linearized output suitable for conversion into a standard 4 to 20 milliamp (mA) direct current (DC) signal typically used in modern industrial instrumentation systems. This signal is used to indicate whether a portion of a rotating machine (e.g., a motor or compressor) is in need of repair or maintenance. The signal may also be used to provide protection to the machine by triggering an alarm indicating vibration levels that exceed a prescribed threshold, thereby allowing an external control system or other mechanism to shut down the machine before the occurrence of a catastrophic failure.
Unfortunately, there may be events detected which could trigger an alarm, but which may be a spurious spike generated by a non-vibration induced random occurrence; in effect, a false alarm. For example, if a metallic particle breaks loose from the machine and travels between the target and the probe of a proximity sensor via, for example, lubricating oil, a non-periodic, random spike may be generated by the proximity transmitter system. Such an event generally resolves itself without a need to shut down the machine.